Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) in children: a randomized controlled trial.

BACKGROUND: Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) was introduced to adult anaesthesia to improve the safety of airway management during apnoea before intubation. The objective of our study was to determine whether THRIVE safely prolongs apnoeic oxygenation in children. METHODS: This was a randomized controlled trial in 48 healthy children, with normal airways and cardiorespiratory function, in age groups 0-6 and 7-24 months, 2-5 and 6-10 yr old, presenting for elective surgery or imaging under general anaesthesia. All children were induced with sevoflurane, O2, and N2O, followed by muscle relaxation with rocuronium, and standardized preoxygenation with bag-and-mask ventilation. The control arm received jaw support during apnoea, whereas the THRIVE arm received jaw support during apnoea and age-specific flow rates. The primary outcome was to demonstrate that children allocated to THRIVE maintain transcutaneous haemoglobin saturation at least twice as long as the expected age-dependent apnoea time in the control group. RESULTS: Both study arms (each n=24) were similar in age and weight. The apnoea time was significantly shorter in the control arm: average 109.2 (95% CI 28.8) s in the control arm and 192 s in the THRIVE arm (0-6 months), 147.3 (95% CI 18.9) and 237 s (7-24 months), 190.5 (95% CI 15.3) and 320 s (2-5 yr), and 260.8 (95% CI 37.5) and 430 s (6-10 yr), respectively. Average transcutaneous haemoglobin saturation remained at 99.6% (95% CI 0.2) during THRIVE. Transcutaneous CO2 increased to a similar extent in both arms, with 2.4 (95% CI 0.5) mm Hg min-1 for the control arm and 2.4 (95% CI 0.4) mm Hg min-1 for the THRIVE arm. CONCLUSION: Transnasal humidified rapid-insufflation ventilatory exchange prolongs the safe apnoea time in healthy children but has no effect to improve CO2 clearance. CLINICAL TRIAL REGISTRATION: ACTRN12615001319561.

Reduced intubation rates for infants after introduction of high-flow nasal prong oxygen delivery.

PURPOSE: To describe the change in ventilatory practice in a tertiary paediatric intensive care unit (PICU) in the 5-year period after the introduction of high-flow nasal prong (HFNP) therapy in infants <24 months of age. Additionally, to identify the patient subgroups on HFNP requiring escalation of therapy to either other non-invasive or invasive ventilation, and to identify any adverse events associated with HFNP therapy. METHODS: The study was a retrospective chart review of infants <24 months of age admitted to our PICU for HFNP therapy. Data was also extracted from both the local database and the Australian New Zealand paediatric intensive care (ANZPIC) registry for all infants admitted with bronchiolitis. RESULTS: Between January 2005 and December 2009, a total of 298 infants <24 months of age received HFNP therapy. Overall, 36 infants (12%) required escalation to invasive ventilation. In the subgroup with a primary diagnosis of viral bronchiolitis (n = 167, 56%), only 6 (4%) required escalation to invasive ventilation. The rate of intubation in infants with viral bronchiolitis reduced from 37% to 7% over the observation period corresponding with an increase in the use of HFNP therapy. No adverse events were identified with the use of HFNP therapy. CONCLUSION: HFNP therapy has dramatically changed ventilatory practice in infants <24 months of age in our institution, and appears to reduce the need for intubation in infants with viral bronchiolitis.

Regional ventilation distribution in the first 6 months of life.

Electrical impedance tomography (EIT) has been used to study regional ventilation distribution in neonatal and paediatric lung disease; however, little information has been obtained in healthy newborns and infants. Data on regional ventilation distribution and regional filling characteristics were obtained using EIT in the neonatal period, at 3 and 6 months of age, in spontaneously breathing infants during non-rapid eye movement sleep. Regional ventilation distribution was described using regional end-expiratory and end-inspiratory impedance amplitudes, and geometric centre of ventilation. Regional filling characteristics were described with the phase lag or lead of the regional impedance change in comparison to global impedance change. 32 infants were measured in the supine position. Regional impedance amplitudes increased with age but regional ventilation distribution remained unchanged in all infants at any age, with the dependent (posterior) lung always better ventilated. Regional filling characteristics showed that the dependent lung filled during inspiration before the nondependent lung during all follow-up measurements. Regional ventilation distribution and regional filling characteristics remained unchanged over the first 6 months of life, and the results obtained on regional ventilation distribution are very similar to those in adult subjects.

The effect of endotracheal suction on regional tidal ventilation and end-expiratory lung volume.

PURPOSE: To examine the impact of different endotracheal tube (ETT) suction techniques on regional end-expiratory lung volume (EELV) and tidal volume (V(T)) in an animal model of surfactant-deficient lung injury. METHODS: Six 2-week old piglets were intubated (4.0 mm ETT), muscle-relaxed and ventilated, and lung injury was induced with repeated saline lavage. In each animal, open suction (OS) and two methods of closed suction (CS) were performed in random order using both 5 and 8 French gauge (FG) catheters. The pre-suction volume state of the lung was standardised on the inflation limb of the pressure-volume relationship. Regional EELV and V(T) expressed as a proportion of the impedance change at vital capacity (%Z (VCroi)) within the anterior and posterior halves of the chest were measured during and for 60 s after suction using electrical impedance tomography. RESULTS: During suction, 5 FG CS resulted in preservation of EELV in the anterior (non-dependent) and posterior (dependent) lung compared to the other permutations, but these only reached significance in the anterior regions (p < 0.001 repeated-measures ANOVA). V(T) within the anterior, but not posterior lung was significantly greater during 5FG CS compared to 8 FG CS; the mean difference was 15.1 [95% CI 5.1, 25.1]%Z (VCroi). Neither catheter size nor suction technique influenced post-suction regional EELV or V(T) compared to pre-suction values (repeated-measures ANOVA). CONCLUSIONS: ETT suction causes transient loss of EELV and V(T) throughout the lung. Catheter size exerts a greater influence than suction method, with CS only protecting against derecruitment when a small catheter is used, especially in the non-dependent lung.

Optimized temperature and deadspace correction improve analysis of multiple breath washout measurements by ultrasonic flowmeter in infants.

BACKGROUND: Assessment of lung volume (FRC) and ventilation inhomogeneities with ultrasonic flowmeter and multiple breath washout (MBW) has been used to provide important information about lung disease in infants. Sub-optimal adjustment of the mainstream molar mass (MM) signal for temperature and external deadspace may lead to analysis errors in infants with critically small tidal volume changes during breathing. METHODS: We measured expiratory temperature in human infants at 5 weeks of age and examined the influence of temperature and deadspace changes on FRC results with computer simulation modeling. A new analysis method with optimized temperature and deadspace settings was then derived, tested for robustness to analysis errors and compared with the previously used analysis methods. RESULTS: Temperature in the facemask was higher and variations of deadspace volumes larger than previously assumed. Both showed considerable impact upon FRC and LCI results with high variability when obtained with the previously used analysis model. Using the measured temperature we optimized model parameters and tested a newly derived analysis method, which was found to be more robust to variations in deadspace. Comparison between both analysis methods showed systematic differences and a wide scatter. CONCLUSION: Corrected deadspace and more realistic temperature assumptions improved the stability of the analysis of MM measurements obtained by ultrasonic flowmeter in infants. This new analysis method using the only currently available commercial ultrasonic flowmeter in infants may help to improve stability of the analysis and further facilitate assessment of lung volume and ventilation inhomogeneities in infants.

Impact of depth of propofol anaesthesia on functional residual capacity and ventilation distribution in healthy preschool children.

BACKGROUND: Propofol is commonly used in children undergoing diagnostic interventions under anaesthesia or deep sedation. Because hypoxaemia is the most common cause of critical deterioration during anaesthesia and sedation, improved understanding of the effects of anaesthetics on pulmonary function is essential. The aim of this study was to determine the effect of different levels of propofol anaesthesia on functional residual capacity (FRC) and ventilation distribution. METHODS: In 20 children without cardiopulmonary disease mean age (SD) 49.75 (13.3) months and mean weight (SD) 17.5 (3.9) kg, anaesthesia was induced by a bolus of i.v. propofol 2 mg kg(-1) followed by an infusion of propofol 120 microg kg(-1) min(-1) (level I). Then, a bolus of propofol 1 mg kg(-1) was given followed by a propofol infusion at 240 microg kg(-1) min(-1) (level II). FRC and lung clearance index (LCI) were calculated at each level of anaesthesia using multibreath analysis. RESULTS: The FRC mean (SD) decreased from 20.7 (3.3) ml kg(-1) at anaesthesia level I to 17.7 (3.9) ml kg(-1) at level II (P < 0.0001). At the same time, mean (SD) LCI increased from 10.4 (1.1) to 11.9 (2.2) (P = 0.0038), whereas bispectral index score values decreased from mean (SD) 57.5 (7.2) to 35.5 (5.9) (P < 0.0001). CONCLUSIONS: Propofol elicited a deeper level of anaesthesia that led to a significant decrease of the FRC whereas at the same time the LCI, an index for ventilation distribution, increased indicating an increased vulnerability to hypoxaemia.

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children.

Caudal block results in a motor blockade that can reduce abdominal wall tension. This could interact with the balance between chest wall and lung recoil pressure and tension of the diaphragm, which determines the static resting volume of the lung. On this rationale, we hypothesised that caudal block causes an increase in functional residual capacity and ventilation distribution in anaesthetised children. Fifty-two healthy children (15-30 kg, 3-8 years of age) undergoing elective surgery with general anaesthesia and caudal block were studied and randomly allocated to two groups: caudal block or control. Following induction of anaesthesia, the first measurement was obtained in the supine position (baseline). All children were then turned to the left lateral position and patients in the caudal block group received a caudal block with bupivacaine. No intervention took place in the control group. After 15 min in the supine position, the second assessment was performed. Functional residual capacity and parameters of ventilation distribution were calculated by a blinded reviewer. Functional residual capacity was similar at baseline in both groups. In the caudal block group, the capacity increased significantly (p < 0.0001) following caudal block, while in the control group, it remained unchanged. In both groups, parameters of ventilation distribution were consistent with the changes in functional residual capacity. Caudal block resulted in a significant increase in functional residual capacity and improvement in ventilation homogeneity in comparison with the control group. This indicates that caudal block might have a beneficial effect on gas exchange in anaesthetised, spontaneously breathing preschool-aged children with healthy lungs.

Prospective randomised treatment with recombinant human growth hormone in cystic fibrosis.

AIM: To evaluate the efficacy and safety of treatment with recombinant growth hormone (rGH) in patients with cystic fibrosis (CF). METHODS: Twenty patients with CF (aged 10-23 years) were randomised to age and sex matched treatment and control groups. The treatment group received daily subcutaneous injections of 1 IU/kg/wk rGH for 12 months. Pulmonary function (forced expiratory volume in one second (FEV1) and airway resistance), exercise capacity measured with a bicycle ergometer, body composition (dual energy x ray absorptiometry), and weight were assessed at the beginning of the study and after 6 and 12 months. RESULTS: rGH treatment did not improve weight and pulmonary function, but lean body mass increased significantly in the treatment group. Exercise capacity increased in the treatment group from 143 (16) W (mean (SD)) to 164 (19) W after 12 months of rGH treatment. CONCLUSION: Treatment of CF patients with rGH for one year improved the exercise capacity significantly but not pulmonary function. The improved exercise capacity needs confirmation in a larger population before such an expensive treatment is justified.

Measurement of lung volume and ventilation distribution with an ultrasonic flow meter in healthy infants.

Small airway disease in infants is characterised by abnormal lung volume and uneven ventilation distribution. An inert tracer gas washin/washout technique using a pulsed ultrasonic flow meter is presented to measure functional residual capacity (FRC) and ventilation distribution in spontaneously breathing and unsedated infants. With a pulsed ultrasound sent through the main stream of the flow meter, flow, volume and MM of the breathing gas can be calculated. Sulphur hexafluoride was used as a tracer gas. In a mechanical lung model (volume range 53-188 mL) and in 12 healthy infants (aged 38.3+/-9.2 days; mean+/-SD) accuracy and reproducibility of the technique was assessed. Indices of ventilation distribution such as alveolar-based mean dilution number (AMDN) and pulmonary clearance delay (PCD) were calculated. Mean error of volume measurement in the lung model was 0.58% (coefficient of variance (CV) 1.3%). FRC was in the low predicted range for normal infants (18.0+/-2.0 mL x kg(-1)) and highly reproducible (5.5+/-1.7% intra-subject CV). AMDN was 1.63+/-0.15 and PCD was 52.9+/-11.1%. Measurement of functional residual capacity and ventilation distribution using a sulphur hexafluoride washin/washout and an ultrasonic flow meter proved to be highly accurate and reproducible in a lung model and in healthy, spontaneously breathing and unsedated infants.

Role of lung function testing in the management of mechanically ventilated infants.

The mechanical characteristics of the ventilated lung can only be interpreted when the volume of the lung, the elastic properties, and the degree of airway obstruction have been accurately quantified by pulmonary function testing. More gentle ventilation strategies (permissive hypercapnia) are used, and the efficacy of mechanical ventilation can be verified in the intensive care unit. Pulmonary function testing brings new insights, awareness, and applications, but its limitations need to be taken into account when interpreting the acquired data.

Cardiopulmonary exercise parameters in children with atrial septal defect and increased pulmonary blood flow: short-term effects of defect closure.

UNLABELLED: Markedly increased pulmonary blood flow because of a relevant atrial septal defect (ASD) leads to impaired cardiopulmonary function during maximum exercise in adults. No comparative preoperative and postoperative data are available on the short-term effects of shunt closure on cardiorespiratory function at peak exercise in children. Pulmonary function testing at rest and cardiopulmonary exercise testing together with haemodynamic assessment was done prospectively in children with an ASD preoperatively and again after full recovery at 3-4 mo postoperatively and compared with a matched normal population. Sixteen children, aged 6.8-16.1 y, with a defect of 8-23 mm (median 15 mm) and a pulmonary/systemic flow ratio of 1.5-3.5 (median 2.2) were tested and compared with 15 healthy children. Preoperatively, baseline pulmonary function parameters and exercise capacity were no different from normals. At peak exercise, patients with a shunt had increased pulmonary resistance, especially of the distal airways (p = 0.04), with a significantly larger proportion of children having a paradoxical increase in total airway resistance during exercise (p < 0.05). Maximum serum lactate at peak exercise was elevated (p < 0.05) in patients. In patients, maximum oxygen uptake was impaired (p = 0.03) and remained so at repeat evaluation postoperatively. The same observation was made for chronotropic response to exercise. CONCLUSION: Cardiopulmonary exercise parameters in patients with ASD differed only slightly from those in normal children. The most important deviations were a lower maximum oxygen uptake and an increase in airway resistance at maximum exercise.

High morbidity and mortality in cystic fibrosis patients compound heterozygous for 3905insT and deltaF508.

Genotype-phenotype association in cystic fibrosis (CF) is difficult because of heterogeneous disease expression. The genotype-phenotype correlation for the 3905insT mutation in comparison to deltaF508 was studied here. Thirty CF patients compound heterozygous for 3905insT were compared to clinical presentation of matched patients homozygous for deltaF508 (1960-1997). Sweat tests, age at diagnosis, at death and at onset of Pseudomonas aeruginosa colonization were analysed. Chrispin-Norman scores and pulmonary function forced expiratory volume in one second (FEV1) determined severity of lung disease. Twenty-five of the patients with 3905insT had deltaF508 as a second mutation and five had another rare mutation. At the age of 15 yrs, 60% of patients with 3905insT had an FEV1 < 60% predicted in comparison to 25% of patients with deltaF508 (p<0.05). Age at death and cumulative survival rate was significantly lower (p<0.05) in the 3905insT than in the deltaF508 group (20.3 and 24.0 yrs, respectively). Age at onset of P. aeruginosa colonization was not different in the study groups. Sweat chloride concentrations were lower in patients homozygous for deltaF508 (105.63+/-15.3 mmol L(-1)) than in patients with 3905insT (119.9+/-22.1 mmol x L(-1)) (p<0.05). Patients compound heterozygous for 3905insT have similar high morbidity and mortality to patients homozygous for deltaF508.

An isoflow-volume technique for assessing airway dynamics in children and adults.

BACKGROUND: We propose a new approach to the measurement of small airway function as an alternative to recordings of maximal expiratory flow-volume (MEFV) curves. OBJECTIVES: A newly developed technique to record isoflow-volume (IFV) curves to be tested against maximal respiratory flow curves. METHODS: An isoflow whistle (IFW; Iflopen) measures the length of a constant expiration after full inspiration. The note of the whistle enables a subject to generate an even expiration, and the isoflow maintenance times at 1 l x s(-1) (IFMT1) and 2 l x s(-1) (IFMT2) are recorded. The accuracy and reproducibility of the IFV technique were evaluated in 17 healthy adults (age 17-55 years) and in 14 asthmatic children (age 6-14 years). Comparisons with standard lung function parameters, such as forced expiratory volume in 1 s (FEV1), maximal expiratory flow at 50% (MEF50) and 25% (MEF25) vital capacity and peak expiratory flow (PEF), obtained with a Wright Peakflow Meter were undertaken in 102 healthy (aged 8-14 years) and 101 asthmatic children (aged 6-17 years). A bronchial challenge test was performed in 13 asthmatic children. RESULTS: The expired volume measured by the IFW showed an acceptable agreement with that of a pneumotachograph (mean error of 4.32% for IFMT1 and 5.93% for IFMT2). In healthy and in asthmatic children, the correlations between FEV1 and IFMT1 or IFMT2 (r = 0.92 and 0.94, respectively) were found to be greater than that between FEV1 and PEF (r = 0.68). During bronchial challenge tests in 13 asthmatic children, the FEV1 decreased to 69% of baseline and IFMT1 to 58% of baseline. CONCLUSIONS: The IFV technique accurately measured airway obstruction and closely followed changes in standard parameters of the MEFV curve.

Measurement of functional residual capacity in rabbits and children using an ultrasonic flow meter.

A sulfur hexafluoride (SF(6)) washin/washout technique was developed using an ultrasonic flowmeter to measure functional residual capacity (FRC) during mechanical ventilation. The ultrasonic flowmeter measures simultaneously flow and molar mass of the mainstream gas. Ventilation distribution was studied using moment ratios analysis (alveolar-based mean dilution number). Accuracy and precision of the measurement technique were tested in a mechanical lung model, and the method's sensitivity to changes of FRC was assessed in seven ventilated rabbits and six children. In the mechanical lung model with a volume range from 10 to 60 mL, the mean error of FRC measurement was 0.096 +/- 0.9 mL (range, 0-2 mL). In seven rabbits (mean body weight, 3.6 kg), measurements of FRC and alveolar-based mean dilution number were made at positive end-expiratory pressures (PEEP) of 0, 3, and 6 cm H(2)O. The mean coefficient of variation of 66 FRC-measurements was 5.5% (range, 0-15.3%). As the applied PEEP increased, mean FRC per kilogram body weight increased from 13.3 +/- 3.4 mL/kg (PEEP of 0 cm H(2)O) to 16.7 +/- 3.6 mL/kg (PEEP of 3 cm H(2)O) and to 20.8 +/- 4.3 mL/kg (PEEP of 6 cm H(2)O). Alveolar-based mean dilution number decreased accordingly from 1.94 +/- 0.42 (PEEP = 0; mean +/- SD), to 1.91 +/- 0.45 (PEEP = 3) and to 1.59 +/- 0.35 (PEEP = 6). In the six children, as applied PEEP increased, mean FRC per kilogram increased from 21.1 +/- 4.51 mL/kg (PEEP = 0), to 22.4 +/- 1.8 mL/kg (PEEP = 5) and 27.2 +/- 3.4 mL/kg (PEEP = 10). FRC measurement using the ultrasonic flowmeter is accurate and simple to use in ventilated and spontaneously breathing children.

Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome in childhood: a report of ten cases and review of the literature.

UNLABELLED: Chronic recurrent multifocal osteomyelitis is a rare chronic inflammatory musculoskeletal process observed in children and young adults. Recently, the acronym SAPHO syndrome (for synovitis, acne, pustulosis, hyperostosis, osteitis) was coined to emphasise the association between osteo-articular inflammations and different skin abnormalities which are aseptic and filled with neutrophils. In adults, chronic recurrent multifocal osteomyelitis is now a classical manifestation of SAPHO syndrome. Chronic skin disorders were seen in eight of ten children on follow-up at the University Children's Hospitals in Bern and Zurich and in 61 of 260 paediatric cases reported in the literature. The different skin lesions were palmoplantar pustulosis (n = 40), non-palmoplantar pustulosis (n = 6), psoriasis vulgaris (n = 16) or severe acne (n = 4). More rarely Sweet syndrome (n = 2) or pyoderma gangrenosum (n = 1) were reported. CONCLUSION: The synovitis, acne, pustulosis, hyperostosis, osteitis syndrome is pertinent even in paediatrics since skin involvement is frequent.

Moment ratio analysis of multiple breath nitrogen washout in infants with lung disease.

Measurement of lung volumes at end expiratory level and assessment of ventilation inhomogeneity is important for respiratory management in infants with lung disease. This study compared multiple breath nitrogen washout was compared with body plethysmography to measure functional residual capacity in infants and assessed ventilation inhomogeneity using mean dilution numbers and alveolar based gas dilution numbers. Measurements were performed in 23 infants with lung disorders, eleven had wheezing bronchitis, four bronchopulmonary disease, and eight cystic fibrosis. Mean age was 11.2+/-5.8 months. Functional residual capacity of nitrogen washout (29.8+/-11.4 mL x kg(-1)) was significantly (p<0.05) lower than the plethysmographically measured functional residual capacity (40.3+/-11.4 mL x kg(-1)). Tidal volumes before nitrogen washout (90.4+/-35.1 mL) were significantly larger than at the end of the washout (72.2+/-26.9 mL). Alveolar based gas dilution numbers (6.7+/-2.3) were significantly lower (p<0.001) than mean dilution numbers (10+/-5.7). Functional residual capacity determination by nitrogen washout and plethysmography in infants with lung disease showed evidence of air trapping and ventilation inhomogeneity. Ventilation inhomogeneities are best described by alveolar based dilution numbers, since rebreathing of 100% oxygen changes ventilation pattern.

[PFAPA syndrome: periodic fever, adenitis, pharyngitis and aphthous stomatitis]. / PFAPA-Syndrom: periodisches Fieber, Adenitis, Pharyngitis und aphthöse Stomatitis.

A syndrome involving periodic fever, pharyngitis, adenitis and aphthous stomatitis is described in 8 children. Attacks are characterized by abrupt onset of fever and, in addition to the above symptoms, by malaise, headache and abdominal pain. Mild leukocytosis and elevation of the erythrocyte sedimentation rate are found in the laboratory. Patients exhibit normal growth and development and are otherwise healthy. PFAPA is clinically benign, with no long-term sequelae. Recognition and diagnosis of the syndrome eliminate the need for intensive work-up. The cause remains unknown. No evidence linking bacterial, viral, or fungal pathogens to this syndrome has been found. No patient has exhibited atypical lymphocytosis or neutropenia, and all patients had normal levels of immunoglobulin. All had received antibiotics early in the course of their illness but without effect. Cimetidine has been discussed in the literature as a possible treatment, but the results are controversial.

Plasma ionized magnesium during acute hyperventilation in humans.

1. Respiratory alkalosis accompanies the clinical syndrome of tetany, precipitates cardiac arrhythmias and predisposes to coronary vasoconstriction. Magnesium plays a critical role in the maintenance of membrane function, and magnesium depletion is often associated with cardiac arrhythmias or vasoconstriction. 2. As technology for detecting circulating ionized magnesium (the most interesting form with respect to physiological and biological properties) is now available in the form of new magnesium-selective electrodes, the effect of respiratory alkalosis induced by voluntary overbreathing for 30 min on circulating ionized magnesium was studied in eight healthy subjects. 3. The total plasma magnesium concentration was not modified by hyperventilation. On the contrary, hyperventilation was associated with a significant reduction in the ionized magnesium concentration of 0.05 (0.02-0.15) mmol/l (median and range) and in the free magnesium fraction of 0.06 (0.01-0.19). During hyperventilation the relative intravascular magnesium mass, calculated from changes in total plasma magnesium concentration and haematocrit, decreased significantly. 4. It is concluded that acute overbreathing reduces the circulating ionized magnesium concentration and the intravascular magnesium mass. It is therefore conceivable that extracellular magnesium deficiency is at least a subsidiary cause of the syndrome of tetany and the cardiac complications that are precipitated by hyperventilation.

Pressure oscillations after flow interruption in relation to lung mechanics.

The value of interrupter resistance measurements has been questioned because these depend on equilibration between alveolar (PA) and mouth pressure (PAO), which may not occur during airway obstruction or in measurements in children. In order to determine whether airway geometry and its interaction with the lung volume can be obtained without complete pressure equilibration, the postocclusional oscillatory airway opening pressure transients PAO(t) after flow interruption were studied in comparison to airway resistance (RAW), lung volumes (TGV, VC) and MEF50 in 9 healthy children (7-14 y) and 5 adults (28-37 y) in both time and frequency domains. The frequency of pressure oscillations was correlated to TGV (p < 0.01). Its damping properties (d) were correlated to MEF50 (p < 0.005). Performing airflow interruptions in the same subject showed that d increased at low lung volumes. During bronchial challenge test, d significantly increased with carbachol and decreased with salbutamol, whereas the frequency decreased with carbachol and increased with salbutamol. Therefore, the analysis of postocclusional pressure oscillations can be used to assess relative changes in airway mechanics and its interaction with lung volume during bronchial challenge tests in patients such as children with poor cooperation.

A new method for assessing flow-volume measurements by means of a simple isoflow electronic pocket device (IfloPen).

The IfloPen is a new device for measuring isoflows featuring specific information about the effort-independent part of the flow-volume curve. Whereas the recording of the latter normally requires expensive equipment, the IfloPen is a handy, portable and simple device. In addition, the isoflow technique requires minimal cooperation. Significant correlations have been found between the isoflow-points measured with the IfloPen and PF, MEF50, MEF25 and FEV1 (p < 0.001). The IfloPen showed better correlations with spirometric lung function data than with the Peak-flow-Meter. Even experimentally induced bronchial obstruction during a bronchial challenge with carbachol can be measured functionally by the IfloPen, showing similar changes as obtained by the FEV1 and the MEF50 (p < 0.001). From a practical point of view, the IfloPen features a new device to measure more accurately bronchial obstruction (no overestimation, physiological breathing maneuver, good practicability). It can therefore be used in medical practice and is a suitable device for home monitoring.